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27 Sep 2010

Volume 97, Issue 13, Articles (13xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 133303 (2010); http://dx.doi.org/10.1063/1.3491815 (3 pages)

Yoshihide Fujisaki, Yoshiki Nakajima, Daisuke Kumaki, Toshihiro Yamamoto, Shizuo Tokito, Takahiro Kono, Jun-ichi Nishida, and Yoshiro Yamashita
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Optimized surface-emitting photonic-crystal terahertz quantum cascade lasers with reduced resonator dimensions

Gregoire Sevin, Daivid Fowler, Gangyi Xu, Francois H. Julien, Raffaele Colombelli, Suraj P. Khanna, Edmund H. Linfield, and A. Giles Davies

Appl. Phys. Lett. 97, 131101 (2010); http://dx.doi.org/10.1063/1.3489941 (3 pages) | Cited 3 times

Online Publication Date: 27 September 2010

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Terahertz frequency photonic-crystal quantum cascade lasers allow directional and controllable surface emission while at the same time functioning efficiently well above liquid nitrogen temperature. Through an in-depth understanding of the mechanism underlying surface emission, we demonstrate optimized devices with significantly reduced absolute threshold currents. We are able to reduce the device surface area by more than a factor of two, while maintaining angularly narrow, single-lobed surface emission with a divergence of ≈ 10°×10°. The devices emit at ∼ 2.8–2.9 THz, with maximum operating temperatures in the range 80–150 K.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Tv Photonic crystal lasers and coherent effects
42.70.Qs Photonic bandgap materials

Turn-on delay and Auger recombination in long-wavelength vertical-cavity surface-emitting lasers

N. Volet and E. Kapon

Appl. Phys. Lett. 97, 131102 (2010); http://dx.doi.org/10.1063/1.3488013 (3 pages)

Online Publication Date: 27 September 2010

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Measuring the turn-on delay of diode lasers provides useful information on carrier recombination dynamics, particularly Auger recombination, essential for their design for high-speed modulation and power-efficient performance. Here we present a rigorous, comprehensive relationship between the time delay and the Auger recombination coefficient. We demonstrate the application of this formulation by extracting this coefficient for AlGaInAs/InP quantum wells incorporated in long-wavelength vertical-cavity surface-emitting lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
79.20.Fv Electron impact: Auger emission
79.60.Bm Clean metal, semiconductor, and insulator surfaces
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Slowing surface plasmon polaritons on plasmonic coupled cavities by tuning grating grooves

Sinan Balci, Askin Kocabas, Coskun Kocabas, and Atilla Aydinli

Appl. Phys. Lett. 97, 131103 (2010); http://dx.doi.org/10.1063/1.3495781 (3 pages) | Cited 6 times

Online Publication Date: 28 September 2010

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We investigate slow surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by coupled plasmonic cavities on Moiré surfaces. We demonstrate controlling the group velocity and dispersion of the SPPs by varying the depth of the plasmonic Bragg grating groove. Changing the grating depth results in modification of coupling coefficients between the cavities and hence the SPPs group velocity is altered. Variation in the group velocity and dispersion of SPPs can be measured with polarization dependent spectroscopic reflection measurements. Dispersion of SPPs has been calculated by finite-difference time-domain method in agreement with the experimental data.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Dj Gratings

Three-color nonlinear optical mixing for the determination of the refractive index dispersion of a tellurite glass

Zhian Jin, Carolyn Kan, Urszula B. Szafruga, Jean Toulouse, and Ivan Biaggio

Appl. Phys. Lett. 97, 131104 (2010); http://dx.doi.org/10.1063/1.3492850 (3 pages) | Cited 2 times

Online Publication Date: 28 September 2010

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We determine the refractive index dispersion of a quaternary tungsten-tellurite glass over a broad spectral range from 0.4 to 3 μm from the wavelength dependence of the phase matching conditions for third-order nonlinear optical frequency conversion. We discuss the optimum phase-matching geometries for this task and obtain the wavelength-dependence of the refractive index to within three significant digits by a least-squares fit of a Sellmeier-type equation to the phase-matching data.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Ce Glasses, quartz

Drooping as a simple characterization tool for extraction efficiency and optical losses in light emitting diodes

Jani Oksanen and Jukka Tulkki

Appl. Phys. Lett. 97, 131105 (2010); http://dx.doi.org/10.1063/1.3494085 (3 pages) | Cited 2 times

Online Publication Date: 28 September 2010

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We extend the previous droop models developed for InGaN light emitting diodes (LEDs) by accounting for the light extraction and show that drooping can be used to quantify both the extraction efficiency and the optical losses in LEDs. Our model allows very simple characterization of LEDs by an integrating sphere and therefore provides an attractive characterization tool to measure the most important loss parameters of various LED structures. In particular, the approach allows evaluation of the effects of various optical losses and photon recycling on the efficiency and consequently allows more efficient optimization of the LED structures. As an additional benefit, our measurement method does not necessarily require any fitting of the data.
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85.60.Jb Light-emitting devices

A tunable universal terahertz filter using artificial dielectrics based on parallel-plate waveguides

Rajind Mendis, Abhishek Nag, Frank Chen, and Daniel M. Mittleman

Appl. Phys. Lett. 97, 131106 (2010); http://dx.doi.org/10.1063/1.3495994 (3 pages) | Cited 9 times

Online Publication Date: 29 September 2010

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Using parallel-plate waveguides (PPWGs) that mimic artificial dielectrics, we demonstrate a universal filter that provides low-pass, high-pass, band-pass, and band-stop (or notch) filtering functionalities in the terahertz (THz) frequency regime. The device essentially consists of two PPWGs in a complementary geometry. The filtering functionality is achieved by positioning an appropriate amplitude mask in the path of the spatially chirped THz beam between the two waveguides. By varying the position of the mask, we experimentally and theoretically demonstrate continuous tunability of the respective 3 dB cutoff frequencies within the frequency range from about 0.3 to 0.7 THz.
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84.30.Vn Filters
84.40.Az Waveguides, transmission lines, striplines
84.40.Dc Microwave circuits
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials

Uniaxial epsilon-near-zero metamaterial for angular filtering and polarization control

L. V. Alekseyev, E. E. Narimanov, T. Tumkur, H. Li, Yu. A. Barnakov, and M. A. Noginov

Appl. Phys. Lett. 97, 131107 (2010); http://dx.doi.org/10.1063/1.3469925 (3 pages) | Cited 10 times

Online Publication Date: 29 September 2010

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We describe a unique class of metamaterials that exhibit strong uniaxial anisotropy with epsilon-zero response along the optical axis and which optical properties depend strongly on polarization. In an example of array of silver nanowires grown in anodic alumina membrane, the proposed singular uniaxial metamaterial is shown to function as a polarizer and narrowband angular transmittance filter.
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42.70.-a Optical materials

A nearly instantaneous gain response in quantum dash based optical amplifiers

A. Capua, G. Eisenstein, and J. P. Reithmaier

Appl. Phys. Lett. 97, 131108 (2010); http://dx.doi.org/10.1063/1.3494528 (3 pages) | Cited 6 times

Online Publication Date: 29 September 2010

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We describe a unique phenomenon occurring in InAs/InP quantum dash amplifiers: a nearly instantaneous gain response taking place across the entire inhomogeneously broadened gain spectrum. The phenomenon is induced by a 100–150 fs pulse and is observable using multiwavelength pump probe measurements. Large bias levels and an intense pump pulse are imperative for enacting the ultrafast mechanism which is due to a combination of the gain inhomogeneity, nonlinear two photon absorption and the quantum wirelike density of state function.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Wd Fiber lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Light propagation in a free-standing lithium niobate photonic crystal waveguide

R. Geiss, S. Diziain, R. Iliew, C. Etrich, H. Hartung, N. Janunts, F. Schrempel, F. Lederer, T. Pertsch, and E.-B. Kley

Appl. Phys. Lett. 97, 131109 (2010); http://dx.doi.org/10.1063/1.3496040 (3 pages) | Cited 8 times

Online Publication Date: 30 September 2010

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We report on the light propagation in a one-line-defect photonic crystal waveguide (W1 PhC WG) patterned into a 450 nm thick free-standing lithium niobate membrane by ion-beam enhanced etching. The Bloch wave vectors and transmission spectrum of this PhC WG were retrieved from optical near-field images. The experimental data show good agreement with simulations performed with the three-dimensional (3D) finite-element method and the 3D finite-difference time-domain method. Those results are promising for the development of integrated optics devices operating at telecom wavelengths and based on free-standing lithium niobate PhC membranes.
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42.82.Et Waveguides, couplers, and arrays
42.70.Qs Photonic bandgap materials
81.65.Cf Surface cleaning, etching, patterning

Integrated silicon optofluidic ring resonator

Genni Testa, Yujian Huang, Pasqualina M. Sarro, Luigi Zeni, and Romeo Bernini

Appl. Phys. Lett. 97, 131110 (2010); http://dx.doi.org/10.1063/1.3496027 (3 pages) | Cited 5 times

Online Publication Date: 1 October 2010

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The feasibility of an integrated silicon optofluidic ring resonator is demonstrated. Liquid core antiresonant reflecting optical waveguides are used to realize a rectangular ring resonator with a multimode interference liquid core coupler between the ring and the bus waveguide. In this configuration the same waveguide used to confine the light is able to deliver the liquid sample without the need for any additional microfluidics, resulting in a very compact device with a required liquid volume of about 0.11 nl. Optical characterization shows that ring with a good quality factor (Q ∼ 800) can be achieved in good agreement with the numerical results.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

GaAs/Al0.15Ga0.85As terahertz quantum cascade lasers with double-phonon resonant depopulation operating up to 172 K

Robert W. Adams, Karun Vijayraghavan, Qi Jie Wang, Jonathan Fan, Federico Capasso, Suraj P. Khanna, A. Giles Davies, Edmund H. Linfield, and Mikhail A. Belkin

Appl. Phys. Lett. 97, 131111 (2010); http://dx.doi.org/10.1063/1.3496035 (3 pages) | Cited 6 times

Online Publication Date: 1 October 2010

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We report the design and performance of GaAs/Al0.15Ga0.85As terahertz quantum cascade lasers with double-phonon resonant depopulation and a vertical lasing transition. Devices were processed into gold-clad double-metal waveguides. Lasing at 3 THz was observed up to a heat-sink temperature of 172 K, which compares favorably with the performance of single-phonon resonant depopulation devices based on vertical lasing transitions. These results demonstrate that terahertz quantum cascade lasers based on double-phonon depopulation designs may be a viable alternative to single-phonon depopulation designs for achieving high-temperature operation.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.60.-q Optoelectronic devices
84.40.Az Waveguides, transmission lines, striplines

Broad area photonic crystal distributed feedback quantum cascade lasers emitting 34 W at λ ∼ 4.36 μm

B. Gökden, Y. Bai, N. Bandyopadhyay, S. Slivken, and M. Razeghi

Appl. Phys. Lett. 97, 131112 (2010); http://dx.doi.org/10.1063/1.3496043 (3 pages) | Cited 9 times

Online Publication Date: 1 October 2010

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We demonstrate room temperature, high power, single mode, and diffraction limited operation of a two dimensional photonic crystal distributed feedback quantum cascade laser emitting at 4.36 μm. Total peak power up to 34 W is observed from a 3 mm long laser with 400 μm cavity width at room temperature. Far-field profiles have M2 figure of merit as low as 2.5. This device represents a significant step toward realization of spatially and spectrally pure broad area high power quantum cascade lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Tv Photonic crystal lasers and coherent effects

Fiber-connectorized micropillar cavities

Florian Haupt, Sumant S. R. Oemrawsingh, Susanna M. Thon, Hyochul Kim, Dustin Kleckner, Dapeng Ding, Donald J. Suntrup, III, Pierre M. Petroff, and Dirk Bouwmeester

Appl. Phys. Lett. 97, 131113 (2010); http://dx.doi.org/10.1063/1.3493187 (3 pages)

Online Publication Date: 1 October 2010

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We present a cryogenically compatible method for permanently connecting and coupling a single mode fiber to a single mode of a micropillar cavity with embedded quantum dots (QDs). Efficient coupling of up to 40% was measured which requires a 300 nm positioning accuracy that remains preserved during the fiber attachment procedure and during cool-down to 4 K. Fiber coupling, as opposed to conventional free space coupling, makes it possible to connect many such QD-cavity systems within the same cryostat which can interact through an external optical network, facilitating the implementation of hybrid photon/confined-electron schemes for quantum communication and information processing.
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42.81.Bm Fabrication, cladding, and splicing
42.82.Ds Interconnects, including holographic interconnects
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Analysis of InGaN-delta-InN quantum wells for light-emitting diodes

Hongping Zhao, Guangyu Liu, and Nelson Tansu

Appl. Phys. Lett. 97, 131114 (2010); http://dx.doi.org/10.1063/1.3493188 (3 pages) | Cited 32 times

Online Publication Date: 1 October 2010

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The design of InGaN-delta-InN quantum wells (QWs) leads to significant redshift for nitride active region with large electron-hole wave function overlap (Γe_hh) and spontaneous emission rate. The analysis was carried out by using self-consistent six-band k⋅p band formalism. The design of active region consisting of 30 Å In0.25Ga0.75N QW with InN delta-layer leads to large Γe_hh of >50% with emission wavelength in the yellow and red spectral regimes, which is applicable for nitride-based light-emitting diodes.
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78.67.De Quantum wells
85.60.Jb Light-emitting devices
71.20.Nr Semiconductor compounds
73.21.Fg Quantum wells

C-band electromodulation in silicon–germanium ring and linear devices

Peng Huei Lim, Jingnan Cai, Yasuhiko Ishikawa, and Kazumi Wada

Appl. Phys. Lett. 97, 131115 (2010); http://dx.doi.org/10.1063/1.3496469 (3 pages)

Online Publication Date: 1 October 2010

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We report C-band electromodulation in waveguide-integrated silicon–germanium (SiGe) ring and linear devices. With a 7 V peak-to-peak, 5 MHz sinusoidal input, a waveguide absorption change of 14.9 cm−1 for the linear modulator, and 3.26 cm−1 for the ring were calculated, corresponding to respective modulation depths of 30% and 0.7%. A 2.6×10−5 ring index change was also noted using a technique capable of resolving minute electrorefraction, even with simultaneous electroabsorption and background attenuation. Our results deliver a proof-of-concept for SiGe field-effect devices using optical interference, which may be suitable for high speed and low power optical switches.
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42.79.Hp Optical processors, correlators, and modulators
85.30.Tv Field effect devices
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.82.-m Integrated optics

Nonplasmonic surface enhanced Raman spectroscopy using silica microspheres

Mark S. Anderson

Appl. Phys. Lett. 97, 131116 (2010); http://dx.doi.org/10.1063/1.3493657 (3 pages) | Cited 3 times

Online Publication Date: 1 October 2010

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Surface enhanced Raman spectroscopy is presented using a nonplasmonic mechanism based on whispering gallery modes in silica microspheres. Sensitive Raman analysis of molecular films is demonstrated by using 5–10 μm sized silica spheres. The advantages of this nonplasmonic approach are the active substrate is chemically inert, thermally stable, and relatively simple to fabricate. Applications include trace organic analysis particularly for in situ planetary instruments that require robust sensors with consistent response.
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78.30.Hv Other nonmetallic inorganics

Watt level performance of quantum cascade lasers in room temperature continuous wave operation at λ ∼ 3.76 μm

N. Bandyopadhyay, Y. Bai, B. Gokden, A. Myzaferi, S. Tsao, S. Slivken, and M. Razeghi

Appl. Phys. Lett. 97, 131117 (2010); http://dx.doi.org/10.1063/1.3496489 (3 pages) | Cited 14 times

Online Publication Date: 1 October 2010

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An InP-based quantum cascade laser heterostructure emitting at 3.76 μm is grown with gas-source molecular beam epitaxy. The laser core is composed of strain balanced In0.76Ga0.24As/In0.26Al0.74As. Pulsed testing at room temperature exhibits a low threshold current density (1.5 kA/cm2) and high wall plug efficiency (10%). Room temperature continuous wave operation gives 6% wall plug efficiency with a maximum output power of 1.1 W. Continuous wave operation persists up to 95 °C.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
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A study of eukaryotic response mechanisms to atmospheric pressure cold plasma by using Saccharomyces cerevisiae single gene mutants

Hongqing Feng, Ruixue Wang, Peng Sun, Haiyan Wu, Qi Liu, Jing Fang, Weidong Zhu, Fangting Li, and Jue Zhang

Appl. Phys. Lett. 97, 131501 (2010); http://dx.doi.org/10.1063/1.3491180 (3 pages) | Cited 6 times

Online Publication Date: 29 September 2010

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The mechanisms of eukaryotic cell response to cold plasma are studied. A series of single gene mutants of eukaryotic model organism Saccharomyces cerevisiae are used to compare their sensitivity to plasma treatment with the wild type. We examined 12 mutants in the oxidative stress pathway and the cell cycle pathway, in which 8 are found to be hypersensitive to plasma processing. The mutated genes’ roles in the two pathways are analyzed to understand the biological response mechanisms of plasma treatment. The results demonstrate that genes from both pathways are needed for the eukaryotic cells to survive the complex plasma treatment.
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87.53.-j Effects of ionizing radiation on biological systems
87.16.-b Subcellular structure and processes

Mechanisms of x-ray emission from peeling adhesive tape

E. Constable, J. Horvat, and R. A. Lewis

Appl. Phys. Lett. 97, 131502 (2010); http://dx.doi.org/10.1063/1.3493653 (3 pages) | Cited 3 times

Online Publication Date: 29 September 2010

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It has previously been reported that x-rays are emitted when adhesive tape is peeled in a vacuum but no account of the dependence of the x-ray emission on the pressure of the environment has been given to date. In this paper we present detailed experimental data on the number and angular distribution of x-ray photons as a function of pressure. We find that x-rays are emitted for pressures between p0 = 10−3 and p1 = 10−2 mBar, with ∼ 106 counts/(cm2 s) recorded by a 256×256 pixel2 silicon array sensor placed 35 mm from the tape. The main role of the tape is found to be the build-up of an acceleration potential sufficient to produce x-rays by bremsstrahlung of free electrons in a low-pressure gas. The source of the free electrons is the gas. Our model shows that the production rate of uncompensated tape charge and absorption of positive ions from the gas define p1. The angular distribution of the radiation shows a pressure-independent 20° wide peak in the direction perpendicular to electron motion. Ordinary bremsstrahlung cannot describe this peak.
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78.70.Ck X-ray scattering
46.55.+d Tribology and mechanical contacts
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Structural origin of the intermediate phase in Ge–Se glasses

G. Chen, F. Inam, and D. A. Drabold

Appl. Phys. Lett. 97, 131901 (2010); http://dx.doi.org/10.1063/1.3495775 (3 pages) | Cited 4 times

Online Publication Date: 27 September 2010

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We have conducted x-ray absorption near-edge structure (XANES) experiments on germanium selenide glasses, in search of a structural signature of the intermediate phase (IP). Quantitative analyses of the XANES spectra reveal compositional plateaus that coincide with the IP reversibility window, providing structural evidence for the IP. Molecular dynamic simulations have been performed to understand the atomistic origin of the electronic structure of the glasses. The IP originates from a competition between amorphous GeSe2 and amorphous Se clusters and produces measurable signatures. Our study provides atomistic insight into the structural origin of the IP in Ge–Se glasses.
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64.70.dg Crystallization of specific substances
64.70.Q- Theory and modeling of the glass transition
78.70.Dm X-ray absorption spectra
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
71.23.Cq Amorphous semiconductors, metallic glasses, glasses

A numerical method for designing acoustic cloak with homogeneous metamaterials

Weiren Zhu (朱卫仁), Changlin Ding (丁昌林), and Xiaopeng Zhao (赵晓鹏)

Appl. Phys. Lett. 97, 131902 (2010); http://dx.doi.org/10.1063/1.3492851 (3 pages) | Cited 8 times

Online Publication Date: 27 September 2010

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Based on the form invariance of Helmholtz equation, we present a rhombic acoustic cloak constructed with homogeneous metamaterials. In free space, the proposed cloak can effectively conceal an object inside under a given incident direction. Another application, namely carpet cloak, was also demonstrated by full wave simulations. The proposed cloak provided great convenience in the fabrication process due to the spatially uniform of relative density and modulus tensors.
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43.20.El Reflection, refraction, diffraction of acoustic waves
43.20.Fn Scattering of acoustic waves

Origins of size-dependent lattice dilatation in tetragonal Sn nanowires: Surface stress and growth stress

Ho Sun Shin, Jin Yu, Jae Yong Song, Hyun Min Park, and Yong-Sung Kim

Appl. Phys. Lett. 97, 131903 (2010); http://dx.doi.org/10.1063/1.3493179 (3 pages) | Cited 1 time

Online Publication Date: 27 September 2010

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Through experiments and theoretical analyses, we demonstrate that Sn nanowires can shrink or expand when the radius decreases from 120 to 1.2 nm. Single crystalline nanowires manifest [100]-longitudinal lattice dilatations that originate from the strong anisotropy of the surface stress. Compressive growth stress, which is generated in the radial direction during the growth of nanowires within templates, leads to greater elongation due to the Poisson effect. The surface stress-induced lattice strains are intrinsic, whereas the growth stress-induced lattice strains can be released. For polycrystalline nanowires, lattice contractions occur because the anisotropy of surface stresses is effectively reduced.
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81.07.Gf Nanowires
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dj Poisson's ratio
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Stability, geometry, and electronic structure of an alternative I-III-VI2 material, CuScS2: A hybrid density functional theory analysis

David O. Scanlon and Graeme W. Watson

Appl. Phys. Lett. 97, 131904 (2010); http://dx.doi.org/10.1063/1.3491179 (3 pages)

Online Publication Date: 27 September 2010

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Cu based I-III-VI2 materials have received much attention due to their utility in solar cell applications. The vast majority these studies have focused on materials with group IIIA cations as the trivalent metal. In this study we utilize the screened hybrid exchange functional, HSE06, to investigate the stability of CuScS2 in the crystal structures of all the other I-III-VI2 materials, and find that it preferentially forms in its own unique structure. We analyze the electronic structure and optical properties of CuScS2 and in light of this discuss its semiconducting ability.
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61.66.Fn Inorganic compounds
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Hd Other semiconductors
71.20.Nr Semiconductor compounds

Fabrication of micropillars by laser-induced thermoplastic method

Leyan Wang, Dongxian Zhang, Haijun Zhang, and J. Z. Jiang

Appl. Phys. Lett. 97, 131905 (2010); http://dx.doi.org/10.1063/1.3493180 (3 pages) | Cited 4 times

Online Publication Date: 28 September 2010

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A laser-induced thermoplastic formation technology for three dimension microstructure has been investigated theoretically and experimentally. An experimental system is built up and formation experiments are carried out on different kinds of thermoplastic materials. The appearance dependence of microstructures (micropillars) on the fabricating parameters has been discussed. Critical parameters for microstructure formation are concluded to be laser power, liquid temperature and material absorptance. By analyzing different melting-solidifying conditions, the balance between melting and solidifying velocities has been considered to be necessary for continuous micropillar growth. Based on theoretical analyses, micropillars with better HW ratio and better resolution are demonstrated.
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81.16.-c Methods of micro- and nanofabrication and processing
61.72.-y Defects and impurities in crystals; microstructure
61.41.+e Polymers, elastomers, and plastics
64.70.dj Melting of specific substances
81.30.Fb Solidification
42.62.-b Laser applications

Dye-sensitized solar cells based on anatase TiO2 nanocrystals exposing a specific lattice plane on the surface

Puhong Wen, Zhuoqi Tao, Yoshie Ishikawa, Hiroshi Itoh, and Qi Feng

Appl. Phys. Lett. 97, 131906 (2010); http://dx.doi.org/10.1063/1.3494087 (3 pages) | Cited 2 times

Online Publication Date: 28 September 2010

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Dye-sensitized solar cells (DSCs) using anatase TiO2 nanocrystals exposing a specific lattice plane on the surface were studied. It was found that dye adsorption strongly depends on the lattice plane exposed on the TiO2 nanocrystal surface, which greatly affects DSC performance. TiO2 nanocrystals exposing mainly the (010) plane have a higher dye adsorption capacity and a higher Voc for DSC than normal spherical nanocrystals. TiO2 nanocrystals with a large adsorption constant Kad can yield a high Jsc. The highest Jsc (20.6 mA/cm2) was achieved by using TiO2 nanocrystals with the specific lattice plane on the surface.
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88.40.H- Solar cells (photovoltaics)
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